1. Field of the Invention
This invention relates generally to the field of nanoparticles. More specifically this invention relates to a method of controlling nanoparticle aggregation sizes.
2. Background of the Invention
Particles that have at least one dimension within two orders of magnitude of 10−9 meters are generally considered nanoparticles. Nanoparticles can be thought of as a bridge between individual molecules and solids, as there are small objects that behave as a whole unit in terms of transport and properties. Particularly, due to the small size there are a number of unique properties are displayed by these particles. Quantum dots, hereinafter QDs, are one class of nanoparticles that have been the focus of research and have demonstrated remarkable potential for commercial applications. QDs may exhibit semiconducting, fluorescence, or emissive characteristics. For instance, QDs are being used as suitable alternatives to organic dyes for biological labeling due to their high detection sensitivity and quantum efficiency.
Typically, QDs are composed of inorganic matter and therefore, they are normally insoluble in water. Yet, for use in practical applications, such as biomedical research or substitutes for antimicrobial agents, water solubility is a necessary physical quality. Conventionally, research has been performed to achieve QD water solubility by using various surfactants or ligands. For example, polyvinyl pyrrolidone, hereinafter PVP, is a polymer which is soluble in water. PVP is amphiphilic, having both hydrophobic and hydrophilic components and because it is inert, PVP is safe for ingestion by humans. PVP is used as a binder in many tablets and for applications in the cosmetic industry. This polymer has been used to modify QDs for the purposes of surface passivation and stabilization in non-aqueous systems.
Single QDs and controlled QD aggregate sizes are of particular significance for both commercial applications and fundamental studies of QDs effect on living cells such as bacteria, because different cells may have variable responses to QDs presented at different sizes but possessing the same chemical composition. However, to date, no research has claimed controlled QD aggregate sizes in aqueous solutions favorable for biomedical applications.
Hence, there is a need for new compositions, which could disperse QDs in water without altering the material's chemistry.